244 THE DOMESTIC SHEEP. 



sheep. Wool grows from the skin. Every day the tip of the 

 fiber is pushed higher from its base by the daily growth. Its 

 substance is derived directly from the skin, certain secre- 

 tions from it supplying the bulb or root of the fiber, that is 

 imbedded in what are known as the hair (and of course 

 wool) follicles (see fig. 1). The precise nature of wool 

 may be learned from these figures: 



, Composition of , 



Skin. Wool. Hair Horn. 



Carbon ....5099 50.65 51.53 51.99 



Hydrogen 707 7.03 6.69 6.72 



Nitrogen 18.72 17.71 17.94 17.28 



Oxygen and sulphur 23.22 24.61 23.84 24.01 



As nothing comes of nothing, and everything in the 

 ' world is made up of elements that must be supplied to it for 

 its growth, so with wool. If any part of its elements are 

 wanting in the food, or is diverted by reason of some special 

 disorder of the sheep from the nutrition of the skin, and 

 from this, of the wool, there is a weak spot. The fiber is 

 thin and defective in strength. If the food is in excess at 

 any time, and production of blood is increased, the opposite 

 condition prevails for a time only, for excitement from 

 whatever cause is sure to be followed by a corresponding 

 relapse, and in such a case we find first a thickened fiber, 

 followed by a thin and weak one. This may be for a short 

 time only, as is seen in that part of the fiber on the left, 

 while on the right there is an indication of some lengthened 

 disturbance of the condition. 



Wool is differentiated more especially by its serrated c.r 

 imbricated surface, its length and fineness; and in the Merino 

 by its peculiar waviness or crimp. And in these respects the 

 different breeds vary so considerably that the expert shepherd 

 or wool grower, as well as the wool-sorter and manufacturer, 

 may be able with ease to distinguish the fleece of each breed. 

 The biologist may even trace the mixture of blood far away 

 back by these special peculiarities, and thus it is most im- 

 portant for the breeder to study this matter with care, 

 and examine samples from his flock under some good micro- 

 scope. It is even possible 'to distinguish in the wool of any 

 pure-bred sheep the marks of any ancestor that might have 

 had some special individual characteristic in this respect. 

 This part of this interesting subject will be more fully dis- 



